1. Field of the invention
The invention relates to a self-aligning roller bearing with two rows of symmetrical rollers, an outer ring with a curved outer track, an inner ring with two curved inner tracks, and a guide ring which is provided between the rollers and which is made as a circular ring disk
2. Description of the Related Art
Antifriction bearings which are used to transfer radial and/or axial loads to rotating parts are divided according to the shape of their roller bodies into ball bearings on the one hand, and roller bearings on the other. In roller bearings, it is distinguished between cylinder, barrel-shaped, needle, tapered and self-aligning roller bearings. Self-aligning roller bearings contain two rows of barrel-shaped rollers with roller axes which are tilted relative to the bearing axis. The outer track is hollow-spherical so that in case of alignment faults and when the assigned shaft sags, the rollers can be adjusted in an oscillating manner in the outer track. The profile of the tracks is generally rather narrowly matched to the profile of the rollers. The different embodiments of the self-aligning roller bearings differ both in size itself and also in the size and shape of the rollers. Thus, there are both embodiments with symmetrical rollers and also those with asymmetrical rollers. In addition, there are embodiments with and without rims.
Self-aligning roller bearings have been used for more than fifty years. Due to their high bearing capacity, they have proven effective and are used wherever high impact-like forces must be accommodated and alignment faults and greater sagging of the assigned shaft must be expected. The main applications are heavy rollers and supporting rolls, marine shafts and rudder posts, rock crushers, crankshafts, transmissions, vibrating screens, milk, grinding and crushing machines. Due to the numerous applications, during decades of use of self-aligning roller bearings, attempts have been made again and again to further increase bearing capacity and reduce production costs by structural modifications. Thus, there have been attempts to guide the rollers with a loose guide ring instead of a middle rim permanently connected to the inner ring, or to abandon special guides completely so that the roller are guided solely by a cage. Normally, one such cage is designed to keep the individual rollers of a row of rollers at a uniform distance to one another and thus, to prevent their mutual contact. In a self-aligning roller bearing however, the rollers of the two rows of rollers move under load onto one another so that wear of the cage occurs when the guidance of the rollers is not assumed additionally by a middle rim or a guide ring.
Whenever a fixed middle rim or a loose guide ring is used in a self-aligning roller bearing, in the prior art, this middle rim or this guide ring has a trapezoidal cross section. Thus, German patent 644 181, FIGS. 2 and 3, published in 1937, discloses a self-aligning roller bearing in which a loose guide ring is used to guide the rollers. Here, the width of the trapezoidal guide ring is so large that The rollers are pressed to the sides of the self-aligning roller bearing. U.S. Pat. No. 2,740,675 published in 1956 discloses a self-aligning roller bearing in which there is a loose trapezoidal guide ring located on the inner ring between the rollers of the two rows of rollers. To obtain optimum friction behavior under different radial loads, the width of the guide ring should correspond exactly to the distance between the rollers of the two rows of rollers. Both in the self-aligning roller bearing as patented in German patent 644 181 and also in the self-aligning roller bearing patented in U.S. Pat. No. 2,740,675, the guide ring is designed on the one hand to safeguard the distance between rollers of the two rows of rollers and on the other to prevent crossing of the rollers. U.S. Pat. No. 5,586,826 which just recently issued discloses a self-aligning roller bearing with a trapezoidal guide ring. Here, the friction will be reduced by a special configuration of the rollers.